In modern internal combustion engines, variable valve drives are used to optimize the charging movement in the combustion chamber, with which valve drives different valves strokes can be set at the charge cycle valves of the internal combustion engine. DE 196 11 641 C1, which is incorporated by reference herein, discloses a valve drive of an internal combustion engine which makes it possible to activate a charge cycle valve with a plurality of different lifting cams. For this purpose, a sliding cam with a plurality of cam tracks is mounted on the cam shaft in a rotationally fixed but axially slideable fashion, which sliding cam has a lifting contour into which an activation element, embodied as a pin, of an actuator engages in order to generate axial sliding of the cam. The axial sliding of the cam sets the respective valve stroke.
DE 10 2008 060 166 A1, which is incorporated by reference herein, discloses a valve drive in which a sliding cam, which is mounted on a cam shaft in a rotationally fixed but axially slideable fashion, has a slotted link section with a plurality of grooves, and in which, in order to bring about axial sliding of the sliding cam, an actuator is provided with a plurality of pins which can be activated. The slotted link section has a first, right-handed thread groove and a second, left-handed thread groove which are arranged next to one another on the circumference of the slotted link section and merge with a common run-out groove. The pins of the actuator interact with the grooves of the slotted link section.
In addition, a valve drive is already known in which the grooves of the slotted link section are positioned one behind the other on the circumference of the slotted link section, specifically a first groove for axially sliding the sliding cam in a first direction and a second groove for axially sliding the sliding cam in an opposite, second direction. In this valve drive too, the actuator comprises, in order to bring about the axial sliding of the sliding cam, a plurality of pins which can be activated, specifically a first pin for axially sliding the sliding cam in both directions about a first axial segment, and a second pin for axially sliding the sliding cam in both directions about a second axial segment.
The pins of the actuator, which interact with the grooves of the slotted link section of the sliding cam in order to bring about the axial sliding of the sliding cam, are, as is known from DE 10 2008 060 166 A1, latched in a housing of the actuator by means of latching elements embodied as latching balls, and are therefore secured, wherein, in order to release the latched connection of the pins, the actuator, specifically an electromagnet thereof, is energized in order to cancel the latched connection of the pins in the housing of the actuator which is brought about by means of the latching elements. The pins of the actuator which are released by the energization thereof can be moved axially in the radial direction of the sliding cam or slotted link section of the sliding cam in order to engage in a groove in the slotted link section.
In the multi-stage valve drives which are known from the prior art and whose actuators have a plurality of pins and the slotted link sections of the sliding cam thereof have a plurality of grooves, there is the problem that during the axial adjustment of the sliding cam on the cam shaft, considerable surface pressures occur between the actuator and the sliding cam. In addition, in such valve drives which are known from the practice, relatively wide sliding cams are necessary in order to comply with system tolerances, which results in a heavy weight of the sliding cam and the abovementioned surface pressures increase further. This is disadvantageous.